The present invention relates to a differential for the axle drive of a motor vehicle, having a differential case which carries a drive gear and in which an axle bolt is disposed which carries differential bevel gears, these differential bevel gears meshing with axle shaft gears which are arranged on axle drive shafts, and these gears being constructed as bevel gears.
U.S. Pat. No. 4,084,450, shows a differential of the above type which has a cast differential case to which a flange is cast for the detachable fastening of a driving gear constructed as a ring gear. In two opposite bores of this case, an axle bolt is fitted which carries the differential bevel gears. The axle shaft gears which are assigned to the axle drive shafts mesh with the differential bevel gears and are supported in the differential case. The above-described state of the art represents the conventional construction of today's differentials. With such constructions, the differential case is comparatively heavy and massive because it must transmit the drive torque introduced via the ring gear and must absorb the forces resulting from the obligatory bevel gearing of the differential bevel gears and axle shaft gears. For the mounting of the gears situated on the inside, the case, as in U.S. Pat. No. 4,084,450, is constructed to be divided in a detachable manner or is provided with corresponding openings for the inserting of the gears. Such openings reduce the stiffness of the case and are generally compensated by a correspondingly massive component dimensioning.
An object of the present invention is to provide an improved differential for the axle drive of a motor vehicle which is to be optimized with respect to stiffness, is of a light weight, is low in price and is easy to mount.
This and other objects are achieved by the present invention which provides a differential for the axle drive of a motor vehicle, comprising a differential case which carries a drive gear, an axle bolt disposed in the differential case, differential bevel gears carried by the axle bolt, axle drive shafts and axle shaft gears arranged on the axle drive shafts, the differential bevel gears meshing with the axle shaft gears which are arranged on axle drive shafts, the axle shaft gears being bevel gears, and a cage in which the axle shaft gears are disposed and which absorbs the forces acting in a direction of the axle drive shafts.
When, in the case of a differential of this type, the axle shaft gears are disposed in a cage which absorbs the forces acting in the direction of the axle drive shafts, the differential case is freed from these forces and may therefore have correspondingly smaller dimensions. This leads to a reduction of the weight and the costs of the differential case. The separate cage permits the inserting of the axle shaft gears and of the axle bolt before the whole differential is mounted. This pre-assembling possibility simplifies and shortens the assembly of the differential.
Since the differential case is freed of the forces absorbed in the cage, it may be constructed to be optimized with respect to stiffness for the transmission of the torque introduced via the driving gear which is constructed, for example, as a ring gear, and of the resulting forces. This may be implemented at reasonable cost, for example, by means of deep-drawn, thin-walled sheet metal parts.
In certain embodiments, the differential can be improved when the ring gear is arranged in the area of the longitudinal axis of the axle bolt. As a result, a direct flux of force is ensured from the ring gear to the axle bolt. A particularly simple, low-cost and stiff construction of the differential case is possible when this case comprises two rotationally symmetrical pots. These may be joined directly, for example, in an overlapping manner, in which case the ring gear is undetachably fitted on in the area of the joint, or they may be connected with one another indirectly via the ring gear to which they are joined.
The weight of the differential case can be reduced further and the flux of force can be improved when the axle bolt is disposed in a recess of the ring gear so that the introduced torque is transmitted directly from the ring gear into this bolt. The forces which act in the direction of the axle bolt and which are caused by the bevelled gearing of the gears may advantageously be supported directly in the ring gear or may be supported in a closed flux of force on the axle bolt. In both cases, the differential case is also freed of these forces and may therefore have correspondingly smaller dimensions.
When the axle bolt, being provided with pins on one or on two sides, engages in a floating manner either in recesses of the ring gear or of the differential case, the differential can automatically adjust according to the existing equilibrium of forces. It is therefore particularly insensitive to position tolerances of the bevel gears with respect to one another which, as a result, can be manufactured and positioned with respect to one another in a simple and low-cost manner. Furthermore, smaller differential bevel gears may be used because the forces for each tooth meshing are the same. Depending on the tolerance position and on the equilibrium of forces, the axle bolt may travel slightly into the direction of the axle shafts which necessarily, via the bevel gearing, leads to a slight travelling in the longitudinal direction of the axle bolt.
The additional expenditures for the cage can be limited in that this cage is formed in a simple and elegant manner from circular-disk-shaped segments which support the axle shaft gears and from struts connecting these segments. This type of a cage can be manufactured in one or two pieces as a sheet metal stamping at low cost, and in a low-weight and stiff manner. When it is manufactured in one piece, the stamping is shaped as a cage by a corresponding bending and by being joined at one point. When it is constructed in two pieces, these are bent as identical U-shaped parts and are connected with one another at two points. Furthermore, the above-described differential offers the advantage that the ring gear can be manufactured in a simplified manner because the screwing to the differential case is eliminated, and the ring gear has no distortions as a result of tapholes.
The rotationally symmetrical construction of the pots, together with the elimination of openings for the mounting of the gears, results in a smooth surface which causes low adulteration losses of the differential case revolving in an axle housing which accommodates the differential and its drive.
The closed construction of this differential case offers the possibility of an encapsulating and thus of a separate lubrication of the differential apart from the lubrication required in the axle housing.